Hello
OK back from the USA and confident we can sort this!!
I have unstalled Norton and installed 360-4. For a brief moment it appeared to be working, 3 to 4 seconds, then it stopped and showed the original error.
I will try the windows repair suggestion, but will this wipe my hard drive? I do backup regularly and will do a backup before anything like this, but the link does not clarify if this is a totally clean start.
Thanks again for your help.